Apparatus for the development of light-sensitive material



Oct. 29, 1940. F. w. VON MEISTER El AL .2 5

APPARATUS FOR THE DEVELOPMENT OF LIGHT-SENSITIVE IMPERIAL Filed Oct. 18, 1937 3 Shoots-Shut 1 r %/5 na Y mam w o w? w w k v. a?

9, 19401 F. w. VON MEISTER El AL 2,219,534

APPARATUS FOR IKE DEVELOPMENT OF LIGHT-SENSITIVE IA'I'ERIAL Filed Q61. 18, 1937 3 Sheets-Sheet 2 TTO EY 5 Oct. 29, 1940.

F. W. VON MEISTER ET AL APPARATUS FOR THE DEVELOPIENT 0F LIGHT-SENSITIVE IATERIAL Filed Oct. 18, 1937 3 Shbetw-Sheot 3 lNVENTORS UNITED STATES PATENT OFFICE APPARATUS FOR THE DEVELOPMENT OF LIGHT-SENSITIVE MATERIAL tion of Delaware Application October 18, 1937, Serial No. 169,548

1 Claim.

This invention relates to apparatus for developing light-sensitive material, particularly light-sensitive material which is developed by a dry process in which ammonia or other chemically active developing gas furnishes the developing medium. Apparatus of this type is described in U. S. Patent No. 2,096,015, issued October 19, 1937, of which this application is a continuationin-part. Many types of apparatus have been sugw gested for this purpose. For the most part, these machines are large, cumbersome, inconvenient and expensive to manufacture. It is, therefore, one of the objects of this invention to provide a machine which is relatively light and inexpensive to manufacture and efllcient to operate.

Another of the objects of this invention is to provide an electrical means for heating and vaporizing the ammonia in an ammonia generating tank of the developing apparatus, which electrical heating means will allow of better heat dis-- tribution in the gas chamber or developing chamber, will be inexpensive to manufacture, easier of installation, and readily adaptable to varying conditions. It is well known that the development of certain types of light-sensitive materials is accomplished best in a heated and humid atmosphere. The electrical heating means must, therefore, be so designed as to maintain the temperature above the dew point, particularly in the vicinity of the subject which is being developed. Open wire electrical resistor wire has been used for the construction of such electrical heating means. We have now found that better heat distribution in the gas chamber and improved control of temperatures are cf- 1 fected by constructing the heating elements of a heater wire having a good electrical heat resisting insulation and being enclosed in a metal sheath or tube. Wires of this construction are 40. generally referred to as soil heater cable. An example of the construction of such soil heater cable is as follows: A nicrome heating wire is enclosed in felted asbestos and covered by a lead sheath, the resistance of the wire being such 5 that the heat developed will not destroy'the insulation or melt the lead sheath even in an enclosed space. The safe resistance factor for such wire is about seven watts per foot. Heaters constructed of this metal covered wire are easily installed and are readily adapted to varying conditions. Furthermore, we have found that by connecting such heaters to a manual or time switch, portions of the cable may be short circuited, thus raising the output per foot of the a cable during limited periods of time. This factor is, of course, important in heating up the machine prior to its use. By such an arrangement,

it is possible to get the machine warmed up to operating temperature more quickly. The short circuiting of a portion of the cable by means of a time switch eliminates the necessity of installing costly additional heaters for this function. Furthermore, it is only necessary that the time switch be sufllciently large to handle the switching of the difference in current between the short circuited cable and the entire length. This difference is only a few watts in comparison to the total that would have to be switched if separate heaters for warming up were used.

Other features relating to the manner of gen- 1. crating or supplying the developing gas and preventing its escape, the manner of delivering the developed subject to the operator, and the manner of keeping the endless belt traveling over the guide rollers in a substantially straight path will 20 appear below in the detailed description of our apparatus.

The accompanying drawings represent a preferred embodiment of our invention.

Fig. I is an elevation of the back of the ma- SI chine.

Fig. II is an end view of the machine, with the end plate removed.

Fig. III is a schematic diagram of the electric wiring.

Fig. IV is a longitudinal section of the developing gas generating tank.

Fig. V is a descriptive plan view of the belt and guides.

Fig. VI is a section taken along the line 9-9 a of Fig. V.

Fig. VII is a cross-section of the electric heater cable.

Fig. VIII is a simplified wiring diagram showing the electrical hook up for the essential ele- 0 ments of Fig. III.

Similar reference characters denote similar elements throughout the various views.

Character I represents the developing tank constructed of any suitable metal, having a perfo- I rated curved top, the perforations 2 of which are relatively small in diameter, The developing tank has open ends. The ends of the tank I are closed by clamping the tank between the two end plates 3 of the machine, using heat insulating gaskets, for 50 instance, rubber gaskets 4 over the ends of the tank I, to insure a tight gas-proof joint between the tank and the end plates of the machine, and provide insulation to reduce heat transfer. An endless rubber belt or blanket 5, traveling over ll as. as titans 1 rated up of I, ca driven w the actuating roller l'- which rotates above its:

shaft I, carried by' bearings i4 andll', which latter are mounted on the end plates 8 of the machine. Beltguides Io, rigidly fastened to the end plates 3, prevent the belt from wandering.

These belt guides are slotted and so arranged as to have guide pieces between the top and the bottom guide plates which are at an angle to the traveling edges of the belt, so that when the belt travels or wanders from right to v left, or vice versa, the edge of the belt is led on to the idling roller 8 at an angle, thereby oii'setting the belts tendency to creep or wander. Actuating roller 8' may be driven by any suitable means. The driving means shown in Fig. I comprises a motor ll; mounted on shaft l2 and operating through a flexible coupling H and reduction gear Ill. The driving pulley 9, also mounted on shaft l2, transmits the power to the driving pulley I, mounted on roller shaft I, through the chain It. Only one of the rollers, the back one 6, drives the belt 5. The forward roller 6 is floating, allowing the belt to be pulled snugly over the curved top of the developing tank. An additional idling roller l8, which rides on top of. the endless belt, close to the driving roller 6', is provided in order to increase the surface of the belt which contacts with the driving roller v8'. v

A small closed metal tank I1 is mounted on the outside of one of the end plates, which tank serves as a storage reservoir for the solution of the developing medium, such as aqueous ammonia. This tank is provided with a valve l8 which can be adjusted by adjusting pin l9 to deliver ammonia to the evaporating tray inside the developing tank I, at any desired rate. A drip sight glass 2| is provided underneath the drip valve I8, in order 40 to enable the operator to observe the rate of drip. A drain valve "is provided at the lowest point at the bottom of the developing tank I from which the spent ammonia solution may be drawn off.

There are'three distinct sets of electrical heaters which are connected through a timer switch 250 to provide the heat necessary for initially heating up the apparatus to operating temperature for vaporizing the ammonia, for maintaining the ammonia vapor above its dew point, and for removing residual ammonia fumes from the finished work piece as it passes down the return guide. The heating elements of all three of these sets of heaters are constructed of a heater wire or cable, such as is shown in cross-section in Fig. VII, where 34 is a layer of electrical heat resisting insulation, 35 is a metal sheath or tube, and 33 is the core or current carrying heater wire. Heaters 28 are disposed longitudinally along the bottom of evaporating tray 20. Ammonia solution dripping from leader pipe 21 onto heater elements 28 is evaporated and caused to rise into and fill the gas space of developing tank Heaters 23, designated as upper heaters in the drawings, are disposed immediately under the perforated plate, their function being to maintain the temperature of the ammonia vapor in the immediate vicinity of the work piece above its dew point. Heaters 24' are disposed at the rear of the print return guide 28 immediately adjacent thereto. When the machine is cold and it is desired to put it into operation, the switch 25 and the automatic timer 250 are closed. The latter short circuits a portion of the heater cable raising the output per foot, thus heating up the developing tank to operating tem- Lture has expired, the automatic timer switch opens and 'thenormaloperating functions of the heaters areresumed, that is, supplying heat to the ammonia evaporating tray for vaporizing the v ammonia. supplying heat tothe gas space of the receiving apron 28 attached to the front of the l base 30. The print return guide is, likewise, at-

- tached to the front of the base plate 30 and slopes back gradually curving under the developing tank I, to allow proper clearance and terminating in a position in the rear of the machine adjacent the under-side of the drive roller 6' and the leaving" side of the perforated curved top of tank I. A static remover 3| is attached to this terminal end of the print return guide, which static remover has its free end disposed adjacent the continuous belt 5 in a position immediately below the center of drive roller 6'.

\ An exhaust fan- 32 of any suitable type is provided to maintain a partial vacuum, inside the housing of the machine, to prevent the escape of any leaking gases and also to remove occluded vapors from the developed subject. The machine itself is covered with sheet metal removably bolted to the end plates 3, forming a housing for the working parts and preventing gases from escaping into the room. Suitable ducts may be provided for carrying fumes from the blower of the machine to the outside of the building.

It is thought that our invention and its numerous attendant advantages will be understood from the foregoing description. It is believed quite obvious that various changes can be made, in the arrangement of the various elements, the form, construction and type thereof, without departing from the spirit or the scope of our invention. The particular detailed description outlined above represents a preferred embodiment for the purpose of illustrating the invention, modifications or mechanical departures, which do not impair the operative efliciency of the machine and which fall within the scope of our invention, will, therefore, readily suggest themselves.

Having now particularly described our invention, what we claim is:

In an apparatus for developing light-sensitive material comprising in combination a developing tank having a curved perforated top, an endless belt driven and guided by rollers and adapted to pass over the perforated top of said developing tank, means for actuating the driving roller, electrical heating means constructed of a heater cable consisting of an inside core of straight resistance wire, a layer of electrical heat resisting insulation, and a metal sheath or tube, said heating means being disposed inside the developing tank adjacent the perforated top, a tray adapted to receive and hold aqueous ammonia disposed along a metal sheath or tube, said heating means being disposed along the bottom of said tray, means for delivering aqueous ammonia ,to the said tray,

means for receiving developed prints, electrical heating means constructed of a heater cable consisting of an inside core of straight resistance wire, a layer of electrical heat resisting insulation, and a metal sheath or tube, said heating means being disposed along the back or said print receiving means, and exhaust means tor removing occluded gases from the developed material and other residual gas from the parts of the machine outside the developing chamber and deliver same to the outside.

FREDERICK W. VON MEIST'ER. FREDERICK W. ANDREW. 

